EP4051826A1

EP4051826A1 - Method for compacting an anti-corrosive paint of a turbine engine part

Info

Publication number: EP4051826A1
Application number: EP20807835.2A
Authority: EP
Inventors: Anthony Cyrille GRUNENWALD; Romaric Jean-Marie PIETTE
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2019-10-31
Filing date: 2020-10-27
Publication date: 2022-09-07
Also published as: FR3102687A1; US20220410208A1; WO2021084202A1; FR3102687B1; CN114616292B; CN114616292A

Abstract

The invention relates to a method for compacting an anti-corrosive paint comprising metal particles of a mechanical part (1) such as a turbine engine part, the mechanical part (1) extending along a longitudinal axis X and comprising a radially outer surface covered with a first layer (4, 4') of anti-corrosive paint. According to the invention, the method comprises at least one step of generating a laser beam (11) on the first layer (4, 4') of anti-corrosive paint so as to bring the metal particles into contact and to render the anti-corrosive paint electrically conductive.

Description

DESCRIPTION

TITLE: PROCESS FOR COMPACTING AN ANTI-CORROSION PAINT FOR A TURBOMACHINE PART

Field of the invention

The present invention relates to the field of surface treatments or preparations of mechanical parts against corrosion. It relates in particular to a method for compacting an anti-corrosion paint covering a part, in particular a turbomachine part.

Technical background

Mechanical parts, especially those used in aircraft turbomachines, are exposed to harsh environments in terms of temperatures, corrosive elements, and oxidation reactions. The parts, such as the compressor and / or turbine shafts, are for example made from a steel or a steel alloy with a reduced cobalt content so as to have high mechanical strength. These steels have a high sensitivity to corrosion phenomena which are manifested mainly by the development of corrosion pits which consist of localized and deep attacks. These parts are also subjected to strong mechanical stresses during operation of the turbomachine which can lead to the development of corrosion. The synergistic stress / corrosion effect leads to a significant increase in corrosion phenomena.

Some parts have been covered with a paint resistant to high temperatures and to various corrosive and oxidative elements (kerosene, oil, etc.) so that they are resistant to the environment in which they operate, and in particular to protect them from corrosion. This paint being composed in part of chromium trioxide, has been classified as CMR which stands for Carcinogenic, Mutagenic, Reprotoxic, and is subject to the "REACH" regulation on Registration, Assessment, Authorization and chemical restrictions.

In order to overcome the constraints linked to this regulation, a solution consisting in making the paint anodic has been developed. Examples of this solution are described in documents FR-A1-2991216 and FR-A1 -3040013. In particular, this solution consists in spraying on the surface of the part a liquid paint having an inorganic binder and loaded with metal particles. This paint is projected via a gun handled by an operator or a mechanical arm, and the painted part is then heated in an oven to polymerize the sprayed paint. Then, the polymerized paint undergoes a mechanical action such as compaction in order to bring the metal particles into contact without degrading the cosmetic and physical appearance of the paint depending on the type of compaction carried out. This action makes it possible to achieve electrical continuity between the metal particles of the paint and the metal parts to be treated. The paint layer is thus made dense and electrically conductive to make it a sacrificial layer which will preferentially corrode, instead of the metal of the part to be protected. We are then talking about an anodic paint to designate the sacrificial layer made conductive.

Compaction consists of sandblasting or shot blasting the painted parts after polymerization with particles of white corundum, glass beads, or even plastic particles. However, the particles used for compaction can become embedded in the paint and on the paint surface. In operation, a release or release of these particles may occur, which may damage other parts of the turbomachine (bearings) which are in the path of these particles which may have a very high hardness such as corundum (9, 5 on the MOHS scale).

In order to limit the release of very hard particles, in particular at a very high speed, certain parts are not compacted, which results in a reduction in the anti-corrosion properties of the coating. The other alternative is to cover the compacted anti-corrosion paint with a top coat to contain any particles in the paint, which extends the manufacturing time of the part without taking into account the different steps necessary for the preparation of the part. before, during and after the application of the paint. In addition, controlling the thicknesses of the different layers of paint is tricky and in particular on parts having a complex configuration.

Summary of the invention

The object of the present invention is in particular to provide a simple and effective solution making it possible to ensure densification of an anti-corrosion paint to increase corrosion protection without encrustation of hard particles and while avoiding degradation of the anti-corrosion paint. corrosion.

We achieve this objective in accordance with the invention thanks to a method of compacting an anti-corrosion paint comprising metal particles of a mechanical part such as a turbomachine part, the mechanical part extending along a longitudinal axis X and comprising a radially outer surface coated with a first layer of anti-corrosion paint, the method comprising at least one step of generating a laser beam on the first layer of anti-corrosion paint so as to put contact the metal particles and make the anti-corrosion paint electrically conductive.

Thus, this solution achieves the aforementioned objective. In particular, the use of at least one laser beam avoids having to resort to the use of media (plastics, ceramics, metals, etc.) which may be released or released when the mechanical part is rotated. This type of compaction, causing metal particles based on aluminum to come into contact to obtain electrical conductivity and therefore anti-corrosion properties, is obtained by supplying energy to the surface. This energy input will change the state of the material of the particles so that they agglomerate with each other. The physical integrity of the painting is thus preserved. Finally, this process can be easily automated and makes it possible to overcome the release or release of foreign particles without the need for the application of a top coat and therefore a gain in terms of manufacturing time and cost.

The method also comprises one or more of the following characteristics or steps, taken alone or in combination: the method comprises a step of installing the mechanical part in an enclosure intended to receive an inert gas such as nitrogen or nitrogen. argon. the contacting of the metal particles is determined by heating the metal particles to a temperature threshold value less than or equal to the melting point of the material of the metal particles. the power of the laser beam is between 200 and 1000 W. the laser beam consists of a single beam with an emission wavelength of between 1000 and 1500 nm. the laser beam sweeps the first layer of anti-corrosion paint on the part following a helical path. the method comprises a step of moving the laser beam in a first direction orthogonal to the longitudinal axis X, the mechanical part being rotated around the longitudinal axis and in translation along the longitudinal axis the mechanical part is hollow . the mechanical part comprises a radially internal surface coated with a second layer of anti-corrosion paint, and in that the laser beam is generated inside the mechanical part and reflected inside the mechanical part so in reaching the second layer of anti-corrosion paint, the laser beam sweeping the second layer of anti-corrosion paint following a helical path; the mechanical part is a turbomachine shaft. the method comprises a step of causing the laser source to move in a first direction orthogonal to the longitudinal axis and in a second direction parallel to the longitudinal axis, the mechanical part being rotated around the longitudinal axis. the laser is of the Nd: YAG type. the metallic particles of the paint include aluminum.

The invention relates to a method for producing an anodic coating, the method comprising the following steps: providing a mechanical part with a longitudinal axis, spraying a liquid paint loaded with metal particles on at least one surface of the part mechanical, polymerization of the paint sprayed on the part so as to obtain a layer of anti-corrosion paint intended to protect the part, compacting of the anti-corrosion paint so as to obtain an anodic paint, the compacting comprising at least one projection of 'a laser beam in the direction of said anti-corrosion paint so as to bring the metal particles into contact and to make the anti-corrosion paint electrically conductive.

The invention also relates to the use of a laser beam from at least one laser source to achieve compaction of anti-corrosion paint coating a mechanical part, and in particular a turbomachine part.

The invention also relates to a mechanical part, in particular of a turbomachine covered at least in part with an anti-corrosion paint compacted according to the aforementioned process.

Finally, the invention relates to a compacting installation for carrying out a method for compacting a mechanical part comprising: an enclosure, a mechanical part with a longitudinal axis comprising at least one radially outer surface which is coated with a first layer of anti-corrosion paint comprising metallic particles, the mechanical part being installed in the enclosure, and a compacting device comprising a laser source intended to generate at least one laser beam in the direction of the first layer of paint so as to bring the metal particles into contact and to make the anti-corrosion paint electrically conductive.

Brief description of the figures

The invention will be better understood, and other aims, details, characteristics and advantages thereof will emerge more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given by way of illustration. purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

[Fig. 1] Figure 1 is a schematic view of an axial section of a mechanical part, such as a turbine engine shaft, installed in an enclosure of a compacting installation according to the invention;

[Fig. 2] Figure 2 is a schematic view in radial section of a mechanical part comprising layers of paint on its radially inner and outer surfaces according to the invention;

[Fig. 3] Figure 3 shows the arrangement of the compacting device for rendering a layer of paint, disposed inside a hollow part, electrically conductive according to the invention;

[Fig. 4] Figure 4 schematically shows the path of the laser scanning on a radially outer surface of the mechanical part according to the invention; and [Fig. 5] Figure 5 schematically illustrates an anti-corrosion paint layer with areas thermally affected by the laser according to the invention.

Detailed description of the invention

Figures 1 to 3 respectively show in an axial section, a mechanical part 1, and in particular a mechanical part of an aircraft turbomachine in an installation for compacting an anti-corrosion paint which coats at least one surface of the mechanical part 1.

By mechanical part we mean parts intended to ensure, in service, a mechanical function, which implies that these parts have good mechanical strength as well as good resistance to corrosion and wear. Turbomachine shafts, and in particular compressor and / or turbine shafts are thus examples of non-exhaustive mechanical parts concerned by the invention. Typically, turbomachine shafts are made of a metallic material or a metallic alloy. The metallic material or the metallic alloy comprises steel, for example. As we can see in FIGS. 1 to 3, the mechanical part 1 is a turbomachine shaft which extends along a longitudinal axis X. The turbomachine shaft is here hollow. The shaft comprises a radially outer surface 2 and a radially inner surface 3 opposed along a radial axis Z perpendicular to the longitudinal axis X.

We recall that, prior to the compacting process, the radially outer surface of part 1 is coated with a first layer 4 of anti-corrosion paint illustrated schematically in FIG. 2. The paint is an inorganic paint or any paint comprising particles. metallic. In particular, a liquid paint loaded with metal particles is sprayed onto the surface of the part. Advantageously, the metal particles are aluminum particles. Examples of anti-corrosion paints applied to the surface of parts are those known under the brand Sermetel W® or Maberbind CF®.

After spraying the paint, the coated part 1 is polymerized so that the paint hardens and forms the anti-corrosion paint intended to protect the part.

The anti-corrosion paint is then compacted. For this, the compaction is carried out in a compaction installation 5. By the term compaction, in the present invention, we mean the fact of using an external energy on the surface of the part coated with the layer of paint with metallic particles of so as to at least partially modify the state of the material and to bring the metal particles into contact. In this way, the anti-corrosion paint is densified and the bringing into contact of the metal particles of the paint increases the corrosion resistance of the latter. The paint is made electrically conductive. We then obtain an anodic coating.

The installation 5 comprises a compacting device 6 which is equipped with a head 7 connected to an energy source intended to supply energy to the surface of the first layer 4 of anti-corrosion paint. The energy source is controlled by an electronic control system 8 of the installation. Typically, the electronic control system 8 is equipped with at least one microcontroller 9 and a memory 10 where many parameters during compaction are recorded.

In the present example, the energy source is configured to generate or project at least one primary laser beam 11 onto the paint coating the mechanical part of the turbomachine. The output emission wavelength of the laser beam is between ultraviolet (UV) and infrared (IR). The laser power is between 200 and 1000 Watt (W).

The compacting device 6 is advantageously installed in an enclosure 12 provided for this purpose. The enclosure 12 is closed for example by means of a door through which the part 1 is introduced. The generation of the laser beam 11 is carried out under gas protection in order to avoid any oxidation of the paint during heating or rise in the temperature of the metal particles and to maintain the anti-corrosion properties of the paint. The gas used is an inert gas such as Argon or Nitrogen.

Advantageously, the flow of inert gas is projected by means of at least one nozzle 13 coaxial with the laser beam so that the most critical zone (which directly receives the laser beam) is constantly protected by a neutral atmosphere. The electronic control system 8 is also connected to the nozzle for spraying the flow of inert gas. Alternatively, the flow of inert gas is projected by means of a nozzle which is arranged near the laser beam so that the flow of gas protects the critical area and its surrounding environment as well.

The contacting of the metal particles is determined by heating the metal particles to a temperature threshold value less than or equal to the melting point of the material of the metal particles. In the present example, the melting temperature of the metal particles in the case of aluminum is of the order of 660 ° C. The temperature threshold value below the melting point of the metal is possible thanks to the thermal shrinkage of the binder (contraction of the silicate network) and to the flow of the metal particles.

The heating of the metal particles (and the paint layer) is defined by a focusing of the laser beam and a line energy. In particular, the focusing of the beam is controlled by adjusting the aperture of a diaphragm which allows the size of the laser beam to be managed. Heating of the particle material causes a change in orientation as explained below.

The linear energy (EL) of the laser (known in English by the expression “Linear Energy Density”) is adjusted as a function of the parameters of the paint (thickness, behavior, etc.) and of the conductivity properties thereof. In the present invention, the linear energy corresponds to the ratio between the power of the laser P (expressed in Joule (J) / second (s)) and the scanning speed of the laser V expressed in millimeter (mm) / s. The linear energy is expressed in J / mm. In fact, too low a linear energy could create defects of the lack of bond type between the particles and possibly a degradation of the quality of the conductive properties of the sacrificial layer. Conversely, an energy that is too high could lead to too much melting of the aluminum particles and lead to a heterogeneous layer of the paint (porosities, thickness).

Advantageously, but without limitation, the laser source is of the Nd: YAG type (yttrium-aluminum garnet) doped with neodymium. This type of laser generates energy compatible with the energy requirement for this application. The emission wavelength of the laser beam is of the order of 1064 nanometers (nm). The power of the laser beam is between 200 and 400 Watt (W).

With reference to FIG. 4 and in order to provide uniform conductivity in the paint layer 4, the scanning of the laser on the anti-corrosion paint is carried out in a helical path 110 or in a corkscrew path. The paint here has a thickness of between 20 and 90 µm. The laser beam is applied to the surface of the paint with a coverage rate Re of the order of 10% and a bandwidth Lb of the order of 1 mm. Line energy depends on the source, the focus of the laser beam and the type of paint.

In the present invention, by the expression “helical path” we mean the trace of the laser beam on the anti-corrosion paint corresponding to a translational movement in a first direction and a rotational movement in a plane orthogonal to the first direction of the. laser beam in relation to the workpiece or the workpiece in relation to the laser beam.

In one embodiment, the turbomachine shaft is rotated around the longitudinal axis X and moves along the longitudinal axis and preferably simultaneously. Advantageously, the displacement of the shaft is a translation. For this, the compacting installation 5 comprises an element 14 for rotating the shaft which is mounted on a frame 15. Guide bearings 16 mounted on the frame allow the shaft to be set in rotation relative to the frame. built. The rotating element 14 is advantageously an electric or thermal motor. The motor is connected to the electronic control system 8 which controls the rotation of the motor in one direction or in another direction. Likewise, the laser generation head 7 moves in a direction r which is parallel to the radial axis Z. This is also a translation. In other words, the laser generation head will be fixed in the directions I and t. The terms "" are used to moving the laser head. The head 7 will move in the direction r so as to adjust the focusing of the laser and to adapt to the geometry of the turbomachine shaft. The rotated shaft advances at a predetermined pitch. The pitch may be of the order of 1 mm / revolution. The concatenation of the rotation and the translation of the turbomachine shaft will allow scanning of the laser along the helical path. Advantageously, but without limitation, the electronic control system is connected to the compacting device 6 so as to control the movement of the head 7.

According to another embodiment, the turbomachine shaft is rotated around the longitudinal axis and the head 7 of the compacting device 6 moves in the direction r and in a direction parallel to the longitudinal axis X so in obtaining the scanning of the laser following a helical path.

In the present exemplary embodiment, the radially internal surface 3 of the shaft also comprises a layer of anti-corrosion paint called "second paint layer" 4 "comprising metal particles. This second layer 4 ’of anti-corrosion paint is identical to the first layer 4. Alternatively, the first and second layers 4, 4’ are different.

In order to reach the second layer 4.4 "of paint (located inside the shaft), a deflector 17 is installed inside the turbine engine shaft. The deflection member 17 is pivotally mounted inside the shaft and its pivoting is controlled by the electronic control system 8 to which the latter is connected. Advantageously, the deflection member 17 is a deflection mirror. In this way, the laser beam which arrives on the mirror is reflected on the second layer of paint. The sweeping of this second layer 4 ’of paint is carried out in the same way as for the first layer of paint 4, that is to say following a helical path.

FIG. 5 illustrates a layer 4 or 4 ′ of anti-corrosion paint with aluminum particles having a thickness of the order of 20 to 90 μm. Depending on the focus of the laser beam, it will diffuse more or less throughout the thickness of the paint layer. For example, a focus of 100% generates an area Z1 whose depth is substantially equal to the thickness of the paint layer. On the other hand, a focusing of the order of 40% generates a zone Z2 the depth of which is less than the thickness of the layer 4, 4 ′ of paint. We will now describe the process for compacting the turbomachine part, using the installation 5 described above. The method comprises a step of installing the mechanical part in the enclosure 12. The part is set in rotation by the electronic control system 8. Simultaneously or after the step of setting in rotation, a laser beam is generated on the chamber. layer 4 of paint coating the part 1. The mechanical part 1 is also moved in translation along the longitudinal axis so that the laser sweeps the layer of paint along the helical path. During this generation step, the energy input will make it possible to bring the temperature of the aluminum particles to a value corresponding to that of their melting temperature or to a value lower than this so that the particles are melted. or partially melted and can agglomerate with each other. We understand that this allows a change in orientation or displacement of the metal particles for contact. The particles in contact achieve electrical continuity. Likewise, the inert gas is projected into the enclosure concomitantly with the laser generation step.

Subsequently, the mirror (deflection member 17) is installed inside the hollow part and the second layer 4 ’is scanned with the laser beam also following a helical path.

Claims

1. A method of compacting an anti-corrosion paint comprising metal particles of a mechanical part (1) such as a turbomachine part, the mechanical part (1) extending along a longitudinal axis X and comprising a surface radially outer (2) coated with a first layer (4, 4 ') of anti-corrosion paint, characterized in that the method comprises at least one step of generating a laser beam (11) on the first layer (4 , 4 ') of anti-corrosion paint so as to bring the metal particles into contact and to make the anti-corrosion paint electrically conductive.

2. Method according to the preceding claim, characterized in that it comprises a step of installing the mechanical part (1) in an enclosure (12) intended to receive an inert gas such as nitrogen or argon.

3. Method according to any one of the preceding claims, characterized in that the contacting of the metal particles is determined by heating the metal particles to a temperature threshold value less than or equal to the melting point of the material of the metal particles. .

4. Method according to any one of the preceding claims, characterized in that the power of the laser beam is between 200 and 1000 W.

5. Method according to any one of the preceding claims, characterized in that the laser beam consists of a single beam with an emission wavelength of between 1000 and 1500 nm.

6. Method according to any one of the preceding claims, characterized in that the laser beam sweeps the first layer (4, 4 ’) of anti-corrosion paint on the mechanical part (1) following a helical path.

7. Method according to the preceding claim, characterized in that it comprises a step of moving the laser beam (11) in a first direction orthogonal to the longitudinal axis X, the mechanical part (1) being rotated around of the longitudinal axis X and in translation along the longitudinal axis X.

8. Method according to any one of the preceding claims, characterized in that the mechanical part (1) is hollow.

9. Method according to the preceding claim, characterized in that the mechanical part (1) comprises a radially internal surface (3) coated with a second layer (4 ') of anti-corrosion paint, and in that the laser beam ( 11) is generated inside the mechanical part (1) and reflected inside the mechanical part so as to reach the second layer (4 ') of anti-corrosion paint, the laser beam (11) scanning the second layer (4 ') of anti-corrosion paint following a helical path.

10. A method according to any preceding claim, wherein the mechanical part is a turbomachine shaft.

11. Method according to any one of the preceding claims, characterized in that the laser is of the Nd: YAG type.

12. Method according to any one of the preceding claims, characterized in that the metallic particles of the paint comprise aluminum.

13. Method according to any one of the preceding claims, in which the anti-corrosion paint is applied by spraying a liquid paint loaded with metal particles on at least one surface of the mechanical part and polymerization of the paint sprayed on. the part so as to obtain a layer of anti-corrosion paint intended to protect the part.